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G~[)8J~ DRAFT FINAL DRAFT - 12/19191 The Piedra River supports a variety of game and non.game fish species. Rainbow trout and brown trout are stocked by the Colorado Division of Wildlife. In addition. 1991 population surveys found non-stocked individuals of both species in the maimtem of the river and some of the tributaries. which is an indication of naMa! reproduction. Brook trout, native Colorado River cutthroat. and cutthroat/rainbow hybrids are also present, primarily in the tributaries. Native. non-game species include mottled sculpin. speckled dace. and bluebead sucker. All three of these species require clean, swift water and are imponant foOO sources for river otter and game fish. In Colorado, the bluebead sucker is restricted to the West Slope. Many interdependent elements make up fish habitat. The most obvious are water quantity and quality. Other critical elements are cover, food supply, spawning substrates, and living space. The interrelationships among these elements is dynamic and fish must adapt and respond to a wide range of conditiom including the annual range of streamflow plus periodic tloods and droughts. The habitat factors which enable fish to survive this range of conditions are deep pools, glides, and cover provided by boulders. large woody debris, ledges, and streamside vegetation. These habitat factors are created and maintained in a dynamic equilibrium by this same range of sueamflOW!. The Piedra River bas no known chemical water quality problems and is quite productive (Mangum, 1990). Adequate streamtlow is the most important factor in maintaining cool temperatures in the summer and in limiting the extent of ice formation in the winter. Larger fish will .stack up. in deep pools to comerve energy. Fish will also use cover to avoid or limit exposure to temperature extremes. [n the winter. smaller fish will wedge themselves into cobble substrates to minimize energy expenditure. Brown trout have been observed using flat surlaces of rocks to lie agaimt, thus comerving energy. Trout and the native species will survive in turbid water for limited periods of time. Sediment is of concern when it becomes embedded in the channel substrate because it reduces available spawning habitat. smothers incubating eggs. and retards fry emergence. While spawning requirements differ among the species in the Piedra River, they all require a dean, gravel substrate with little to no embedded fine sediments. Trout and suckers deposit their eggs in redds fanned in gravels near the outlets of pools or behind large boulders. Sculpin and dace deposit their eggs in the spaces between cobbles and the eggs adhere to the rocks. The tribuuries of the Piedra play an important role in spawning; young fish and spawning adults were found in the First Fork and its tribuuries and in Sand and Weminuche Creeks. The perennial tribuuries also have resident trout populations. Many young trout were found in smaller tribuuries such as Sheep. Indian. and O'Neal Creeks during 1991 surveys. These smaller tribuuries are critical for spawning and rearing; adult tish typically do not remain in them after spawning. Brown trout egg incubation occurs when streamtlows are the lowest (November through ~1arch or April). See Figure D. To avoid desiccation of eggs. nows should not be artificially decreased below those which occur at the time of egg deposition. Rainbow trout fry emerge during the high tlows associated with snow melt and their survival is largely dictated by the availability of complex cover. structure. and velocity shelters along the margins of the stream and behind boulders and large cobbles. :0-:0 abrupt reductions in Page 9